A new species of plesiosauroid — a group of long-necked marine reptiles — has just come to the surface in Germany’s Posidonia Shale fossil beds.
This 183 million-year-old plesiosauroid lived during the Age of Dinosaurs (252 million years to 66 million years ago), and experts excavated the remains in 1978 in Holzmaden, Southwest Germany. It wasn't until 2025 that it finally has a name — Plesionectes longicollum.
Read More: Plesiosaur Sheds Light on Marine Reptile Evolution During the Jurassic Period
A Well-Preserved Fossil
According to a new study in Paleontology and Evolutionary Science, the P. longicollum (meaning long-necked near-swimmer) fossil is nearly complete, offering paleontologists a better look and understanding of the marine ecosystems of that time.
The specimen offers not only fossilized bone but also fossilized soft tissues.
"This specimen has been in collections for decades, but previous studies never fully explored its distinctive anatomy," said Sven Sachs of the Naturkunde-Museum Bielefeld, the study's lead author, in a press release. "Our detailed examination revealed an unusual combination of skeletal features that clearly distinguish it from all previously known plesiosaurs."
Oldest Known Plesiosaur in Holzmaden
The Posidonia Shale fossil beds are home to numerous paleontological finds, including ichthyosaur skin. The bed is a great place for well-preserved fossils, so it’s no surprise that P. longicollum is so well intact.
With the identification of this fossil, researchers now know that the area was even richer in biodiversity than previously realized. What's more, this P. longicollum fossil is the oldest known plesiosaur from the Holzmaden area.
According to the press release, researchers have found five other plesiosaur species at the Posidonia Shale fossil beds, including individuals from three major plesiosaur lineages.
View Into the Past
According to the research team, this individual was a juvenile, and despite that, it was developed enough that the researchers could tell it was from a completely new genus and species.
"This discovery adds another piece to the puzzle of marine ecosystem evolution during a critical time in Earth's history," explained study co-author Daniel Madzia in a press release. "The early Toarcian period, when this animal lived, was marked by significant environmental changes, including a major oceanic anoxic event that affected marine life worldwide."
Read More: Species of Ichthyosaur Is Largest Known Marine Reptile at 80 Feet Long
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Paleontology and Evolutionary Science. An unusual early-diverging plesiosauroid from the Lower Jurassic Posidonia Shale of Holzmaden, Germany
Earth Science Reviews. What role does anoxia play in exceptional fossil preservation? Lessons from the taphonomy of the Posidonia Shale (Germany)
A graduate of UW-Whitewater, Monica Cull wrote for several organizations, including one that focused on bees and the natural world, before coming to Discover Magazine. Her current work also appears on her travel blog and Common State Magazine. Her love of science came from watching PBS shows as a kid with her mom and spending too much time binging Doctor Who.
